1. Field of the Invention:
The present invention relates to the preparation of N-(dichlorophosphoryl)trichlorophosphazene [P.sub.2 NOCl.sub.5 ], and, more especially, to the preparation of P.sub.2 NOCl.sub.5 from phosphorus pentachloride and ammonium chloride.
2. Description of the Prior Art:
U.S. Pat. No. 3,231,327 describes the preparation of N-(dichlorophosphoryl)trichlorophosphazene having the Formula (I): ##STR1## from phosphorus pentachloride and ammonium chloride, according to the following reaction scheme: EQU 9PCl.sub.5 +3NH.sub.4 Cl.fwdarw.3P.sub.3 NCl.sub.12 +12 HCl(1.) EQU 3P.sub.3 NCl.sub.12 +2P.sub.2 O.sub.5 .fwdarw.3P.sub.2 NOCl.sub.5 +7POCl.sub.3 ( 2.)
It does not appear from this '327 patent that the grain size distribution of the NH.sub.4 Cl has any effect on the course of the reaction or the nature of the resulting final products. Furthermore, it is recommended to use the NH.sub.4 Cl in a stoichiometric excess of approximately 10% in the reaction with PCl.sub.5. It also appears, however, that the preparation of P.sub.2 NOCl.sub.5 carried out without consideration of the aforementioned parameters, i.e., primarily the grain size distribution of the NH.sub.4 Cl and also the molar ratio of the reagents, gives rise to extremely variable results, in particular relative to the proportion of reagents converted and, secondly, the absence of formation of linear oligomers of the type represented by the formula: EQU [Cl.sub.3 P--N.dbd.PCl.sub.2).sub.n PCl.sub.3 ].sup.+ Cl.sup.-